looking for some good yaoi with yukuza/mafia kind of guys where one's or both are in yukuza/mafia.

Try this search: Link

Here's a list of what I like:
Kizuna
Ikoku Irokoi Romantan
Finder
Boku no Shiru Anata no Hanashi
Bi no Isu
Secret Connection
Heart Strings
Kyou Hana no Gotoshi
Trigger
Twin's Labyrinth
Totally Captivated
Tadayoedo Shizumazu, Saredo Naki mo Sezu, Don't Stay Gold, and Saezuru Tori wa Habatakanai
NightS
1-en no Otoko
Takaga Koi daro, sequel Aiso Tsukashi
Shibuya de Aimashou
Usagi Otoko Tora Otoko
Torawarebito, oneshot
Ake Nure Goyou ni Furu Yuki wa
Tengoku e Ikebaii - ex
Harem Days - ex

MadameRed, I think this is the link you wanted to provide Yaoi + "Mafia" category (There are only 2 titles in the "Yakuza" category.)